Heliophysics Science Division
Sciences and Exploration Directorate - NASA's Goddard Space Flight Center

June 3, 2011, 12:00 pm - 1:00 pm

June 3, 2011, 12:00 pm - 1:00 pm

The Inner and Outer Universe of Magnetic Reconnection



Dr. Seiji Zenitani, NASA Goddard Space Flight Center/JSPS/UMBC

Magnetic reconnection is one of the most important key processes in plasma systems: laboratory, solar, space, and astrophysical plasmas. In this talk we explore basic physics of magnetic reconnection at macroscopic and microscopic scales. First, we discuss large-scale structures of the reconnection system by using resistive MHD simulations. In particular, we investigate MHD structures around a "plasmoid", a big magnetic island in front of the reconnection jet. Employing a high-resolution shock-capturing code, we resolve various new structures: postplasmoid slow shocks, forward slow shocks, shock-reflections, flapping jets due to the KH instability, and so on. Their relevance to the upstream plasma condition is discussed.Next, we visit the reconnection site in collisionless magnetic reconnection. The critical "diffusion region (DR)," where the ideal condition breaks down, is of strong interest for understanding the key mechanism of reconnection. Therefore it is one of the main targets of NASA's Magnetospheric Multiscale (MMS) mission also. Recent researches have reported puzzling electron-scale structures of the DRs, and there is an ongoing debate on their interpretation. We present our answer to this important problem. Using a principle of the invariance, we derive a new measure "D" to identify the DR. It is tested by particle-in-cell simulations: the innermost region surrounding the reconnection site is accurately located in all cases. We further discuss physical significance of our measure and the obtained DR.